1. Field of the Invention
The invention relates to an exhausting structure, and more particularly to an exhausting structure used in a rear projection TV.
2. Description of the Prior Art
In a rear projection TV that becomes popular because of its low price and big screen, images are magnified by optical image projection technology. The image projection needs high-power bulbs as a light source to display with high brightness. Meanwhile, a fan is also needed to cool down the high temperature generated by the operation of the bulb to increase the service life of the bulb. Furthermore, heated optical components can be also cooled down so as to operate with optimal performance.
Referring to FIG 1, a conventional projection TV 10 is mounted inside a casing 11. An optical engine 12 mounted at a bottom of the casing 11 generates image beams that are projected on a front reflector 13, reflected to an upper reflector 14 and then reflected to a front screen 15 to display image frames. In order to dissipate heat generated from the high-power light source and other electronic components in the optical engine 12 50 so as not to accumulate the heat in the rear projection TV 10, a plurality of blowholes (not shown) is formed through the casing 11 to dissipate the heat by convention. The blowholes not only cannot prevent dusts from polluting the optical components, but also has limited dissipation effect due to internal heat recycle. Furthermore, strayed light from high-brightness image beams transmits through the blowholes, adversely affecting the display quality.
Therefore, a fan 16 is further provided on a rear portion of the casing 11 near the optical engine 12. The heat near the optical engine 12 that is a main heat source is forced to dissipate out of the casing 11. The fan 16 can be directly attached on the casing 11 to increase the heat dissipation. The fan 16 generates and spreads noises when in operation. The high-brightness image beams of the optical engine 12 travel through gaps between blades of the fan 16 and then are projected on objects nearby to form reflected lights. The reflected lights may interfere with the user when he or she watches the TV 10 within a dark background. Besides, the back of the TV 10 usually stands away from a wall to prevent the blowholes from being blocked, which limits the spatial arrangement of the TV 10.